Unlike the day or year, the week isn’t tied to any naturally recurring phenomenon. When meteorologists detect a trend that follows a weekly rhythm, they suspect that human activities–and the 5-day work week–are responsible.
In 1998, researchers at Arizona State University in Tempe reported that daily oceanic rainfall shows a weekly precipitation cycle across a stretch of water to the lee of the coastal metropolitan area in the eastern United States. This extreme western part of the North Atlantic Ocean receives significantly more of its precipitation on weekends, they observed. Similar weekly cycles are evident in the concentrations of two pollutants–ozone and carbon monoxide–and in the incidence of tropical cyclones.